Method for encoding and simultaneously decoding images having multiple color components

ABSTRACT

A method is provided for encoding a latent image having at least two color components into a visible image. A first and second image associated with first and second color components, respectively, are generated. The first image has a first pattern of elements and the second image has a second pattern of elements that are manipulated based on a corresponding color component provided in the latent image. A first and a second angle are assigned to the first image and the second image, respectively. The first image and second image are aligned by orienting the first pattern of elements according to the first angle and second angle, respectively. The aligned first image and second image are superimposed to render an encoded image that is decoded using a decoder that simultaneously display the first color component and the second color component of the latent image to present a color composite image.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application61/447,878, filed Mar. 1, 2011 and U.S. Provisional Application61/447,886, filed on Mar. 1, 2011, the complete disclosures of which areincorporated herein by reference in their entirety. This application isa continuation-in part of U.S. application Ser. No. 13/270,738 filed onOct. 11, 2011, which claims priority to U.S. Provisional Application61/391,843, filed Oct. 11, 2010 and U.S. Provisional Application61/461,224, filed on Jan. 14, 2011, the complete disclosures of whichare incorporated herein by reference in their entirety. This applicationis directed to subject matter related to the technology disclosed in thefollowing U.S. Patents, the complete disclosures of which areincorporated herein by reference in their entirety: U.S. Pat. No.5,708,717, issued Jan. 13, 1998, U.S. Pat. No. 7,466,876, issued Dec.16, 2008, U.S. Pat. No. 7,512,249, issued Mar. 31, 2009; and U.S. Pat.No. 7,512,249, issued Mar. 31, 2009.

FIELD OF THE INVENTION

The invention relates generally to the field of counterfeit protection,and more particularly to the field of electronic and printed documentprotection using encoded images.

BACKGROUND OF THE INVENTION

Document falsification and product counterfeiting are significantproblems that have been addressed in a variety of ways. One approach hasbeen using latent or hidden images applied to or printed on articles tobe protected. These latent or hidden images are generally not viewablewithout the assistance of specialized devices that render them visible.

One approach to the formation of a latent image is to optically encodethe image so that, when applied to an object, the image can be viewedthrough the use of a corresponding decoding device. Such images may beused on virtually any form of printed document including legaldocuments, identification cards and papers, labels, currency, andstamps. They may also be applied to goods or packaging for goods subjectto counterfeiting.

Articles to which an encoded image is applied may be authenticated bydecoding the encoded image and comparing the decoded image to anexpected authentication image. The authentication image may includeinformation specific to the article being authenticated or informationrelating to a group of similar articles (e.g., products produced by aparticular manufacturer or facility). Production and application ofencoded images may be controlled so that they cannot easily beduplicated. Further, the encoded image may be configured so thattampering with the information on the document or label is readilyapparent.

In existing systems, when an encoded image is decoded, the hiddencontent is revealed as a monochrome image. Alternatively, the hiddencontent is revealed as an image that has the exact same colors providedin each location of the printed artwork without the decoding device.While the hidden content may appear brighter or darker compared to thevisible content, the image follows the colors present in the visiblecontent. Using prior art methods, it is not possible to design the colorappearance of the hidden content and to encode it in such way that thereis no visual correlation between colors observable with naked eye in thevisible content and colors in the decoded hidden content. What is neededis a process and method of encoding and decoding hidden images using twoor more color components.

SUMMARY OF THE INVENTION

The present disclosure provides a computer-implemented method and systemfor encoding a latent image into a visible image based on encodingparameters, the latent image having two or more color components thatare simultaneously revealed upon placing a decoder over an encodedimage. The decoder includes decoding parameters that match the encodingparameters. The method generates a first image associated with a firstcolor component and a second image associated with a second colorcomponent, the first image having a first pattern of elements and asecond pattern of elements that are manipulated based on correspondingcolor components of the latent image.—A first angle is assigned to thefirst image and a second angle is assigned to the second image. Thefirst image and second image are aligned by orienting the first patternof elements according to the first angle and second angle, respectively.The aligned first image and the aligned second image are superimposed torender the encoded image.

The present disclosure further provides a computer-implemented methodand system for decoding a composite image having a latent image embeddedtherein. The decoded latent image includes first and second colorseparations that are oriented at different angles within the compositeimage, the first and the second color separations being simultaneouslyrevealed by placing a decoder over the composite image. The methodincludes determining a first angle associated with the first colorseparation of the latent image and determining a second angle associatedwith the second color separations of the latent image. A first colorcomponent is assigned to the first color separation based on thedetermined first angle and a second color component is assigned to thesecond color separation based on the determined second angle. A decoderis provided to simultaneously display the first color component and thesecond color component of the latent image in order to present a colorcomposite image.

Another aspect of the disclosure provides a multi-layer decoder fordecoding a composite image having a latent image embedded therein. Thelatent image is encoded into the composite image based on a plurality ofencoding parameters and includes first and second color separations thatare oriented at different angles within the composite image. The firstand the second color separations are simultaneously revealed by placingthe multi-layer decoder over the composite image. The multi-layerdecoder includes a first layer having first elements oriented along afirst angle associated with the first color separation of the latentimage. A second layer is affixed to the first layer; the second layerincludes second elements that oriented along a second angle associatedwith the second color separation of the latent image. The first layerand the second layer are being positioned relative to each other so thatthe first layer and the second layer simultaneously reveal the firstcolor component and the second color component of the latent image topresent a color composite image.

Yet another aspect of the disclosure provides a single-layer decoder fordecoding a composite image having a latent image embedded therein. Thelatent image is encoded into the composite image based on a plurality ofencoding parameters and includes first and second color separations thatare oriented at different angles within the composite image. The firstand the second color separations are simultaneously revealed by placingthe single-layer decoder over the composite image. The single-layerdecoder includes first elements that are oriented along a first angleassociated with the first color separation of the latent image. Secondelements are provided and are oriented along a second angle associatedwith the second color separation of the latent image. The first elementsand the second elements are positioned relative to each other so thatthe first elements and the second elements simultaneously reveal thefirst color component and the second color component of the latent imageto present a color composite image.

Yet another aspect of the disclosure provides a computer-implementedmethod for encoding two latent images into a visible image based onencoding parameters, the latent images having different content that isassociated with two or more color components to generate a rainboweffect that is revealed upon placing a decoder over an encoded image.The decoder includes decoding parameters that match the encodingparameters. The method includes generating a first image associated witha first color component, the first image having a first pattern ofelements that are manipulated based on a corresponding color componentprovided in the latent image. A second image associated with a secondcolor component is generated, the second image has a second pattern ofelements that are manipulated based on a corresponding color componentprovided in the latent image, the second latent image includes differentcontent than the first latent image. The first image and the secondimage are superimposed to render the encoded image, the encoded imagebeing visually similar to the visible image when viewed with an unaidedeye.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be more fully understood by reading the followingdetailed description together with the accompanying drawings, in whichlike reference indicators are used to designate like elements, and inwhich:

FIG. 1 illustrates an example of encoding a latent image having twocolor components into a visible image according to an embodiment of theinvention;

FIG. 2 illustrates an overlay of halftone screens according to anembodiment of the invention;

FIG. 3 illustrates a phase shifted segment for a half tone imageaccording to an embodiment of the invention;

FIGS. 4A-4C are a schematic representation of component images used toproduce a composite image according to an embodiment of the invention;

FIGS. 5A-5B are a schematic representation of component image elementsproduced in a method of producing a composite image according to anembodiment of the invention;

FIG. 6 is a schematic representation of component image elementsproduced in a method of producing a composite image according to anembodiment of the invention;

FIG. 7 illustrates a composite image produced in a method according toan embodiment of the invention;

FIG. 8 is a schematic representation of component images used to producea composite image according to an embodiment of the invention;

FIG. 9 is a flow diagram of a method of producing a composite imageincorporating a latent image according to an embodiment of theinvention;

FIG. 10 is an illustration of component images used to produce acomposite image according to an embodiment of the invention;

FIG. 11 is an illustration of a composite image formed from a visibleimage screened using the composite image of FIG. 10 in accordance with amethod according to an embodiment of the invention;

FIG. 12 illustrates component images formed from a visible image andused to produce a composite image using a method according to anembodiment of the invention;

FIG. 13 illustrates visible and latent component images used to producea composite image using a method according to an embodiment of theinvention;

FIG. 14 is a schematic representation of the elements of a series ofcomponent images used to produce a composite image using a methodaccording to an embodiment of the invention;

FIG. 15 illustrates a visible image and two latent component images usedto produce a composite image using a method according to an embodimentof the invention;

FIG. 16 illustrates a side view, bottom view and top view for a decoderhaving two layers according to an embodiment of the invention;

FIGS. 17A-17C illustrate different configurations for a two layerdecoder according to an embodiment of the invention;

FIG. 18 illustrates an example single-layer decoder that simultaneouslydecodes latent image color components according to an embodiment of theinvention;

FIG. 19 illustrates an example of a single-layer decoder that decodesfrequency sampled color components according to an embodiment of theinvention;

FIG. 20 illustrates a digital decoder that decodes and simultaneouslydisplays latent images encoded having two or more color separationsaccording to an embodiment of the invention;

FIG. 21 illustrates a system for encoding and decoding images such thata composite image encoded with latent images two or more colorcomponents are simultaneously displayed according to an embodiment ofthe invention; and

FIG. 22 illustrates lens element patterns that may be used to viewimages produced using a method of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The disclosure provides methods of encoding and decoding images havingcolor information. The image (hereinafter “composite image”) may includetwo or more latent images that are embedded into a visible image.Alternatively, the composite image may include a latent image having twoor more color separations embedded into the visible image. The compositeimage is placed upon articles that are subject to alteration,falsification and counterfeiting.

In this disclosure, a “latent image” refers to an image that ismanipulated and hidden within the visible image. When the compositeimage is generated from the latent image and the visible image, thelatent image cannot be discerned from the composite image by a humaneye, without the aid of a latent image rendering device (“renderingdevice”) or a decoding device. One or more latent images may be hiddenin the visible image so that the latent image is difficult to discernwithout a rendering device. In an alternative example, the latent imagemay be visible, but not readable, because latent image content issystematically scrambled within the composite image or otherwisemanipulated. This disclosure provides techniques for encoding a latentimage having two or more color components into a visible image. Thisdisclosure further provides techniques for encoding two or more latentimages generated using different color components, into a visible image.The disclosure further provides techniques for simultaneously decodingtwo or more color components associated with the latent images. Stillfurther, the disclosure provides digital techniques for decoding latentimages having color separation information, such as differingorientation angles or other color separation information.

As described herein, latent images may be encoded into visible imagesusing optical cryptography and optical steganography. In thisdisclosure, the term “optical cryptography” describes a process by whicha latent image is “scrambled” (i.e. made unreadable) until a matchingoptical decoder is placed over the composite image to descramble thehidden content.

According to one example, the latent images may be encoded into thevisible image at selected angles for each of the two or more colorcomponents. For half tone latent images, the half tone latent imagesassociated with the two or more color components may be encoded into thevisible image at one or more selected frequencies. The selectedfrequency may be the same for each of the two or more color components.Alternatively, the selected frequency may be different for each of thetwo or more color components. Within each color component, phaseshifting techniques may be applied to embed latent image into thevisible image. For example, half tone segment or line gratings may bephase shifted to account for density patterns of the latent image at aparticular location. The rending device may include elements that areconfigured to correspond to the encoding parameters. For example, halftone encoding parameters may include the selected encoding angles andencoding frequencies. The rendering device may further provide colordepths of the latent image by decoding the density patterns of thelatent image color components. Thus, the latent image becomes visiblewhen the rendering device is placed over the composite image. One ofordinary skill in the art will readily appreciate that techniques otherthan phase shifting may be provided to encode the latent images.

FIG. 1 illustrates an example for encoding a latent image into a visibleimage using two color components. Visible image 110 includes a firstcolor component 112 and a second color component 114. Latent image 116include a heart shaped item 117 generated using a first color component.Latent image 118 include a star shaped item 119 generated using a secondcolor component. The resulting composite image 120 includes the latentimages 116 and the latent image 118 embedded into the visible image 110.Decoded image 122 is revealed upon decoding the resulting compositeimage 120. As discussed below, decoded image 122 shows both the heartshaped item 117 from latent image 116 and the star shaped item 119 fromlatent image 118, displayed simultaneously in their corresponding colorcomponents.

In FIG. 1, the color latent image 116 and the color latent image 118 areencoded separately into the corresponding color component of the visibleimage 110. Encoding for the first color component may be performed byshifting the first color component halftone image by half of thehalftone frequency at sections where there is content inside the firstcolor component of the latent image. For example, the first screenfrequency may be 200 lines per inch and the first screen may be orientedat 75 degrees from a horizontal axis. The encoding of the second colorcomponent may be performed by shifting the halftone image at sectionswhere there is content inside the second color component of the latentimage. The second screen frequency may be 200 lines per inch and thesecond screen may be oriented at 15 degrees from the horizontal axis. Asdiscussed below, the color latent image may be decoded using two layeredrendering device having a first layer that matches halftone parametersof the first screen and a second layer that matches halftone parametersof the second screen. For example, the first screen may correspond tocyan and the second screen may correspond to magenta.

FIG. 2 illustrates an overlay of halftone screens 200. The overlay 200depicts an equal amount of the manipulation of the halftone screens 202,204 at all points having content of the color components of the latentimages. As a result, the decoded latent images will include a consistentor same color intensity level at all positions. This reduces a depth ofeach color components to two levels. A variation of this method may beperformed to encode the color latent images with more tonal levels foreach color component. The quality of the decoded color latent image maybe improved by preserving a color depth of the hidden latent. In otherwords, rather than providing a limited number of phase shifts, such as afull phase shift or no phase shift at a given spot in the decoded latentimage, the color component information may be preserved with finergranularity during the encoding process.

FIG. 3 illustrates an example of phase shifting a segment 301 for ahalftone image to preserve color components using three phase shiftsduring the encoding process. One of ordinary skill in the art willappreciate that any number of phase shifts may be used to representcolor density values between 0-100%. Shift areas are shown, including apartial shift area 310 for 25% color density and a full shift area 315for 100% color density at sections where there is content inside acorresponding color component of the latent image. During a shift, thesegment 301 is moved into a selected area 302 located adjacent to thesegment 301. A no shift area 305 is shown for a latent image sectionthat does not include content.

Expanding on the concept of FIG. 3, an amount of segment shifting may becommensurate to a density value of the latent image at the given spot.For example, if the density value is 100%, a maximum shift of theencoding segment (usually half of the decoder period) may be applied; ifthe density value is 50%, the segment can be shifted by 50% of themaximum possible shift; if the density value is 25%, the segment can beshifted by 25% of the maximum possible shift; and so forth. One ofordinary skill in the art will appreciate that the shifting value may beany increment, such as 10%, 1%, 0.1%, 0.01%, or the like.

An optical decoder will show areas with different amounts of shifting ashaving different densities, thus giving a color depth to the decodedlatent image. According to one example, a maximum color depth and amaximum number of colors that may be encoded may be determined by theratio of printing resolution and encoding resolution. For example, if animage is printed with 2400 dots per inch and if the image is encodedwith 200 lines per inch, a width of the encoding element will be2400/200=20 dots. The full density of the hidden image inside theencoded image is usually achieved when the encoding element is shiftedby one half of its width, i.e. by 10 dots. Thus, by applying shifts of1, 2, . . . , 10 pixels, ten 10 different density levels may be encodedfor each hidden image color separation. This results in a total of 10̂4different colors for a four color printing press. This method may beused to encode high quality color images into the visible image.According to one example, the decoded latent image may appear withimproved quality if this method is used with a monochrome latent image.This is due to the fact that the decoded image may be shown withmultiple brightness levels, instead of a binary image. The abovedescribed concepts also apply to the scrambling examples describedbelow.

In this disclosure, the term “optical steganography” describes a processwhere a plain or cryptographically modified image is used to reform thevisible image by applying different transformations. For example, thesegment line grating associated with the color components may be shiftedto match a pattern of the rendering elements provided on the renderingdevice. The latent image remains invisible to the unaided eye untildecoded by placing a matched rendering device over the visible image.Various techniques may be used to encode and decode latent images andvisible images.

As described in detail below, encoded latent images may be opticallydecoded using a software decoder or a rendering device, such as aphysical lens. The rendering device may include elements arranged inlinear and non-linear patterns. The latent images or latent image colorcomponents may be encoded and decoded using a segment frequency matchinga segment frequency of the rendering device or software decoder. Forexample, the latent image segments are distorted in selected areas tohide the latent image when viewed with the unaided eye. Encoded latentimages may be produced in digital form as described in U.S. patentapplication Ser. No. 13/270,738, filed on Oct. 11, 2011, or in U.S. Pat.No. 5,708,717, issued Jan. 13, 1998, the contents of both of which areincorporated herein by reference in their entirety. Encoded latentimages may be produced in analog form using specialized photographicequipment as disclosed in U.S. Pat. No. 3,937,565, the content of whichis incorporated herein by reference in its entirety.

To enable image authentication, the encoded latent image is embeddedwithin visible images, such as photographs, tint-like images, documents,or the like, to form composite images. The composite image may beprinted on, affixed or associated with articles, including documents,identification cards, passports, labels, products, product packaging,currency, stamps, holograms, or the like. According to one example, theencoded composite images may be produced using visible inks, invisibleinks, special inks, toner, dye, pigment, varnish, a transmittent printmedium, or the like. Alternatively, the encoded composite images may beembossed, debossed, molded, laser etched, engraved, or the like, andaffixed to articles. The composite image serves to authenticate articlesand promotes anti-counterfeiting efforts.

This disclosure describes various techniques for encoding multiplelatent images or a latent image having two or more color components intoa corresponding visible image. Techniques described by the same assigneefor encoding latent images into a visible image include (1) combiningmultiple components to create a composite image, such as described inU.S. patent application Ser. No. 13/270,738, filed on Oct. 11, 2011,which is hereby incorporated by reference in its entirety; (2) usingcryptographic and steganographic methods, such as described in U.S. Pat.No. 7,796,753, issued Sep. 14, 2010,U.S. Pat. No. 7,466,876, issued Dec.16, 2008, U.S. Pat. No. 6,859,534, issued Feb. 22, 2005, and U.S. Pat.No. 5,708,717, issued Jan. 13, 1998,which are hereby incorporated byreference in their entirety; and (3) using stenographic methods, such asdescribed in U.S. Provisional Application 61/447,886, filed on Mar. 1,2011, which this application claims priority to and which is herebyincorporated by reference in its entirety.

Applying A Single Layered Decoding Lens To Decode A Composite ColorImage Created By Combining Multiple Component Images

According to one example, an image to be encoded or scrambled is brokeninto image portions or component images that may include tonalcomplements of one another, for example. The tonal component images maybe balanced around a selected feature, such as a color shade or otherfeature. The component images are sampled based on a selected parameter,such as frequency, and the sampled portions may be configured to providea composite image, which appears to the unaided eye to be a single toneimage, for example. The single tone may be the selected color shade. Aswill be discussed herein, the samples may be arranged according to aparameter defined in a corresponding decoder or rendering device thatmay be used to view the encoded, scrambled or latent image.

In one example, image portions may be extracted from at least twodifferent images. The different images each may contribute imageportions that are encoded or scrambled to render the composite image.The image portions from at least two different images may be encoded orscrambled together to form a single composite image that can be decodedto reveal one or more hidden images.

According to one example, one or more latent images can be “hidden”within a visible image by constructing a composite image as describedherein. The composite image may be transformed to a visible image usingrendering technology such as halftone screens, stochastic methods,dithering methods, or the like. In another example, one or more latentimages may be hidden within the visible image by creating a compositeimage that is derived from samples of component images obtained from thevisible image. The composite image is created by obtaining acomplementary inverse image portion for each corresponding imageportion. The image portion and the complementary inverse image portionmay be patterned in pairs according to a parameter, such as frequency,and multiple pairs may be positioned adjacent to each other to renderthe composite image.

According to one example, encoding is performed by overlaying the latentimage onto the visible image to identify visible image content areasthat correspond to latent image content areas. At these identifiedvisible image content areas, the inverse image content and thecorresponding image content are exchanged or swapped. The encodedcomposite image is obtained by applying this technique to each of theimage portion and the complementary inverse image portion pairs over thecomposite image. This technique enables images to be encoded withoutdividing the latent image into color separations. Thus, this disclosuresupports encoding images by modifying a single parameter of thecomposite image, such as a tone parameter.

After the composite image is digitally generated, the composite imagemay be rendered using halftone screens, for example. Since the latentimage is encoded using a desired frequency for the image portion and thecomplementary inverse image portion pairs, the halftone screens may beprinted at a halftone frequency that is a larger than the desiredfrequency of the image portion and the complementary inverse imageportion pairs. For example, the halftone frequency may be at least twotimes larger than the desired frequency of the image portion and thecomplementary inverse image portion pairs. Furthermore, the halftonescreen angles may be selected to avoid Moiré effects, such as betweenthe printing screen and the encoding element. One of ordinary skill inthe art will appreciate that various larger multiples of halftonefrequency may be used without causing interference to the compositeimage.

One example for generating the composite image includes digitallyencoding a color latent image using an image portion and thecomplementary inverse image portion to generate an encoded tint image.Another example for generating the composite image includes digitallyencoding a darkened and brightened version of the color latent image. Analternative technique for blending colors into the composite imageinclude transforming a color image into a color space that separates theimage into intensity and color components, such as Lab, Yuv, or HSIcolor space. Other color spaces may be used.

After the composite images are digitally encoded, the composite imagemay be printed using standard printing techniques, such as halftonescreen printing, stochastic screen printing, and dither printing, amongother printing techniques. As discussed herein, if halftone printing isused, the halftone frequency may be set to a frequency that is largerthan the frequency of the rendering device or decoder frequency. Forexample, the halftone frequency may be at least two times larger thanthe frequency of the rendering device or decoder frequency. One ofordinary skill in the art will appreciate that various larger multiplesof halftone frequency may be used without causing interference to thecomposite image.

As discussed herein, an encoded image is provided in the form of acomposite image constructed from multiple component images. Thisdisclosure provides methods of using a multiple component approach forhiding information into the composite image.

The use of component images takes advantage of the fact that the humaneye is unable to discern tiny details in an encoded image. The encodedimage is usually a printed or otherwise displayed image. The human eyetends to merge together fine details of the printed or displayed image.As a result, printers are designed to take advantage of this humantendency. Printers produce multitudes of tiny dots or other structureson a printing medium, such as a substrate, paper, plastic, or the like.The size of individual printed dots can be measured as small asthousands of an inch and are not perceived by unaided human vision. Thehuman eye averages the dot patterns to create a color shade. The dotsize or the dot density, for example, will determine the perceived colorshade. If the printed dot sizes are bigger, or if the dots are printedcloser together, the eye will perceive a darker shade. If the printeddot sizes are smaller, or if the dots are printed further apart, the eyewill perceive a lighter shade.

According to one example, the latent image can be broken into tonallycomplementary component images. In this disclosure, the term “tonallycomplementary” describes balancing the component images around aparticular color. Therefore, if corresponding elements, such as elementsfrom corresponding locations on the component images are viewedtogether, the eye will perceive the color around which the componenttones are balanced. The terms tonal values or tonal shade mean eitherintensity value or color value.

FIG. 4A shows first and second component images defining a latent image.In component image 1, a solid background 410 is provided with a firsttonal shade that surrounds an area 420. A second tonal shade is providedto define the latent image depicted by the block letters “USA”. Incomponent image 2, the tonal values are reversed in comparison tocomponent image 1. The second tonal shade covers a background area 410′and the area 420′ defining the block letters “USA” includes the firsttonal shade. The first and second tonal shades are balanced around asingle shade so that if the component images are composite, the nakedeye will perceive only the single shade and the block letters “USA” maynot be discernible. Each component image may be referred to as a “phase”of the original image.

According to one example, each phase can be divided into small elementsaccording to a pattern corresponding to a pattern of the decoder orrendering device. For example, the rendering device patter may bedefined by lens elements. The lens elements may be linear elements(straight or curved) or segments that correspond to the lens elements ofa lenticular lens, for example. Alternatively, the lens elements may beformed in a matrix of two dimensional elements corresponding to amultiple-element lens, such as a fly's eye lens. In the example shown inFIG. 4B, the component images are divided into an array of squareelements 430, 430′. The square elements 430, 430′ may correspond in sizeand position to the elements of a fly's eye lens, for example. Thecomponent element pattern may include a frequency that corresponds tothe frequency (or one of the element frequencies) of the lens elements.The component element pattern may have the same frequency (orfrequencies for a multi-dimensional pattern) as the lens elementfrequency (or frequencies). Alternatively, the component element patternmay have a frequency that is a multiple of the of the lens elementfrequency.

As shown in FIG. 4B, the elements 430, 430′ corresponding to thecomponent image 1 and the component image 2 may be systematicallydivided into subelements 432, 432′. Samples may be taken from thesubelements 432, 432′ and may be combined to form a composite image 440that has an average tone that matches that of the shade around which thecomponent image 1 and the component image 2 are balanced. As illustratedin FIG. 4C, the elements and subelements are so large that the latentimage is readily apparent. It will be understood, however, that if theelements of the composite images are sufficiently small, the human eyewill merge the elements together so that only a single uniform colorshade is perceived.

When a single uniform color shade or tone is viewed by the unaided eye,the composite image may appear not to include content. However, thelatent images become visible when a decoder or rendering device ispositioned over the composite image such that features of the decoderinclude a frequency, a shape and a geometrical structure that correspondto the pattern of the subelements 432, 432′. In practice, the latentimages are decoded when the decoder or rendering device is properlyoriented on the composite image 440. The decoder features are configuredto separately extract portions of the composite image contributed byeach of the component image 1 and the component image 2. This allows thelatent image to be viewed by a human observer looking through thedecoder. The decoder features may include magnifying properties and theparticular component image viewed by the observer may change dependingon an angle of view through the decoder. For example, from a first angleof view, the viewer may see an image having light background with a darkinset. From a second angle of view, the viewer may see an inverse imagehaving dark background with a light inset.

The example component images illustrated in FIGS. 4A-4C include twocolor shades. It will be understood, however, that the number of colorshades is unlimited. According to one example for producing a singleapparent tonal value in the composite image, the various color shadesprovided in the two component images may be balanced around the singletonal value. Alternatively, the component images may be balanced aroundmultiple tonal values, in which case, the resulting composite image willhave multiple apparent tonal values.

According to one example illustrated in FIGS. 4A-4C, the composite imagemay be designed to work with individual lenses, such as fly's eyelenses, arranged in an array, such as a square or rectangular grid. Itwill be understood, however, that the lens features may be formed invirtually any pattern including a symmetric pattern, an asymmetricpattern, a regularly spaced pattern, or an irregularly spaced pattern.Furthermore, the lens feature may be adapted to any shape. The size ofthe composite image elements may be determined by the features sizes ofthe decoding lens. As noted herein, the sampling frequency of thecomponent images may be calculated to be a multiple of the featurefrequency of the decoder. For example, the sampling frequency of thecomponent image may be the same, twice, or three times the samplingfrequency of the lens features.

In the example shown in FIG. 4C, the alternating portions of thecomponent image form the composite image having a matrix pattern thatappears as follows:

-   Component 1 Component 2 Component 1 Component 2 Component 1    Component 2 Component 2 Component 1 Component 2 Component 1    Component 2 Component 1 Component 1 Component 2 Component 1    Component 2 Component 1 Component 2 Component 2 Component 1    Component 2 Component 1 Component 2 Component 1 Component 1    Component 2 Component 1 Component 2 Component 1 Component 2    Component 2 Component 1 Component 2 Component 1 Component 2    Component 1-   It will be understood that other systematic approaches may be    utilized for collecting and ordering portions of the component    images in order to form the composite image and/or the elements    inside the composite image. FIGS. 5A and 5B, for example, illustrate    an approach to collecting and ordering portions of the component    images 500, 500′ to form elements of the composite image 500″. The    component images 500, 500′ may be constructed using tonal values    that are balanced around one or more selected tonal values. The    balanced values may be used to define a latent image.

In the examples illustrated in FIGS. 5A and 5B, the component images500, 500′ are divided into elements 530, 530′ each having a 2×2 patternof subelements 532, 532′. The pattern is similar to the pattern used inthe example of FIG. 4C. It will be understood that while only a singleexemplary element 530, 530′ is shown for each component 500, 500′, thedisclosure supports dividing the entire composite image into a grid ofsuch component images. As illustrated in FIG. 5A, diagonally opposedsubelements A1 and A2 are taken from each element (or cell) 530 of thefirst component image 500. Similarly, the diagonally opposed subelementsB1 and B2 are taken from the corresponding element 530′ of the secondcomponent image 500′. The B1 and B2 portions may be selected so thatthey differ in exact location from the A1 and A2 portions, as shown inFIG. 5A. Alternatively, the B portions may be taken from the samelocations as the A portions as shown in FIG. 5B. In either case, theselected portions are then used to construct a composite image 500″. Inthe example of FIG. 5A, the subelements A1, A2, B1 and B2 all may beplaced in the corresponding element 530″ of the composite image 500′ inthe exact locations from which they were taken. In the example of FIG.5B, the B subelements may be positioned in a slightly different locationin the composite image from where they were taken in order to fill outthe element 530″. In both examples, however, the four subelements A1,A2, B1 and B2 are all taken from the same cell location to assure thatthe corresponding cell 530″ in the composite image 500″ will have thesame apparent tonal value in either case.

It will be understood by those of skill in the art that the subelements532, 532′ may be shapes other than a square shape. For example, thesubelements 532, 532′ may include, but not limited to, any polygon,circle, semicircle, ellipse and combinations or portions thereof. Thecomponent elements 530, 530′ could be divided into two or fourtriangles, for example. The component elements 530, 530′ also may beformed as two rectangles that make up a square element. For images to beviewed using a fly's eye lens, the component elements (or portionsthereof) can be sized and shaped to correspond to the shape of thedecoder features. Any combination of subelement shapes can be used that,when combined, form the corresponding element shape. The disclosurecontemplates mixing different shapes, as long as the desired tonalbalance is maintained. Different sized subelements may also be usedwithin a composite image. Even if a total area belonging to each of theimage components are not equal, any disparity can be compensated byusing a darker or lighter tone for one of the image components. Forexample, for a first image area at 50% having a 60% density associatedwith the first component and for a second image area at 50% having a 40%density associated with the second component will give a 50% overalltint. However, using a first image area at 75% having a 60% densityassociated with the first component and using a second image area at 25%having a 20% density associated with the second component will also beperceived as 50% overall tint density. Another approach includes using adifferent number of subelements from different components. For example,two subelements can be taken from the first component and foursubelements can be taken from the second component, as long as the tonalbalance is maintained. According to these examples, since two componentimages are provided, half of each component image is used to form thecomposite image.

FIG. 6 illustrates an embodiment that produces a scrambling effect inthe composite image. In this approach, overlapping sample portions aretaken from the component images and the sample portions are reduced insize so as to form non-overlapping pieces or subelements of a compositeimage. The difference in sizes between the portions of the componentimage and the subelements of the composite image may be referred to as azoom factor or subelement reduction factor. For example, for a zoomfactor of three, the size of the portions of the component images wouldbe three times larger than the size of the subelements of the compositeimage. In this example, the size of the portions of the component imagesare reduced in size three times before being inserted into the compositeimage.

FIG. 6 illustrates first and second component images 600, 600′, whichare used to construct a composite image 600″. According to one example,overlapping elements 650, 650′ are taken from corresponding componentimages 600, 600′, reduced in size as a function of the zoom factor, andplaced as subelements 632″ within element 630″ to form the compositeimage 600″. It will be understood that although only two suchsubelements are shown for each component image (i.e., A1, A2, B1 andB2), the overlapping elements 650, 650′ cover the entirety of the twocomponent images 600, 600′. Each subelement is positioned based on theconfiguration and frequency of the decoder features and on theconfiguration of the subelements 632″. In the embodiment shown in FIG.7, the overlapping elements are centered on the locations of thesubelements 632″.

In FIG. 6, the shaded area identified as Element A1 in the firstcomponent image is shrunk down three times in each dimension to createsubelement A1 of the composite image (i.e., a zoom factor of 3 isapplied). Subelement A1 is centered on the position corresponding to thecenter of Element A1 in the component image. The large square identifiedas Element A2 is shrunk down three times in each dimension to obtainsubelement A2 of the composite image 600″, which is similarly centeredon the location corresponding to the center of the Element A2. Similaroperations were performed to obtain subelements B1 and B2 of thecomposite image 600″.

The effect of using a zoom factor to create the composite image isillustrated in FIG. 7, which shows a composite image 700 formed from thecomponent images in FIG. 4. The pattern of the elements and thesubelements in the composite image 700 are configured to correspond tothe features of a matching decoder. The composite image of FIG. 7 wasformed using a zoom factor of 4, but it will be understood that thecomposite image may be formed using any zoom factor. Despite thescrambled appearance of the image portions that make up the compositeimage, placement of the matching decoder over the composite imageresults in the “reassembly” of the component images 410, 410′ forviewing by an observer. It follows that the observer will see the latentimage 420, 420′ within the corresponding component images 410, 410′.According to one example, the latent images may appear to move or“float” when as the observer changes his angle of view through thedecoder. This floating effect results from using the overlappingcomponent portions that have been zoomed. The zoom effect causes theelements of the component images to spread into multiple parts of thecomposite image. By adjusting the angle of view, the decoder rendersinformation from the multiple parts of the component image, therebycreating an illusion of floating. Generally, the bigger the zoom factor,the more pronounced the floating effect. On the other hand, by shrinkingthe portions of the component images by a zoom factor, the effectiveresolution of the component images may be decreased when seen throughthe decoding lenses.

In some embodiments of the invention, the elements of the componentimages may be flipped before being used to form the composite image.Flipping portions of the component images changes the direction in whichthese portions appear to float when seen through the decoder. Byalternating between flipping and not flipping the elements of thecomponent images, different parts of the component images may appear tofloat in opposite directions when seen through the decoder.

In certain instances, the above effects may be applied to a singlecomponent image (or two identical component images) that is used toproduce a non-tonally balanced encoded image. Such images could be used,for example, in applications where a decoder lens is permanently affixedto the composite image. In such applications, tonal balancing isunnecessary because the latent image is always viewable through thepermanently affixed decoder.

According to one example, a composite image may be formed from more thanone latent (or other) image. For each such composite image, a pluralityof component images may be created using the methods previouslydiscussed. Portions from each component image may then be used to form asingle composite image. For example, if it is desired to use two latentimages (Image 1 and Image 2), each latent image could be used to formtwo component images. The two component images may each be divided intoelements and subelements as shown in FIGS. 4-6. This would produce fourcomponent images, each having corresponding elements and subelements. Acomposite image similar to those of FIGS. 5A and 5B could be formedusing a subelement A1 taken from a first component of Image 1 and asubelement A2 taken from a second component of Image 1. Similarly, asubelement B1 could be taken from a first component of Image 2 and asubelement B2 from a second component of Image 2. In another example,subelements A1 and B2 could be taken from components of Image 1 andsubelements B1 and A2 could be taken from components of Image 2. Thesubelements could be ordered in multiple ways. For example, thesubelements could be ordered one below another, side by side, across thediagonal from each other, or in any other way. The composite image mayproduce the effect that the human observer may see the different latentimages depending on the angle of view through the decoder. The componentimages may alternate and switch when the angle of view is changed.Additionally, the zoom factor and flipping techniques may be used withthis technique. This may create a multitude of effects available to thedesigner of the composite image. Any number of latent images may behidden together in this manner and any number of component images may beused for each.

According to another example, different zoom factors can be used for thesubelements that are obtained from the different images. For example, azoom factor of two may be used for the subelements obtained from Image 1and a zoom factor of eight may be used for the phases obtained fromImage 2. The subelements obtained from the different images may appearto be at different depths when seen through the decoder. In this way,various 3D effects may be achieved.

FIG. 8 illustrates an approach to collecting and ordering portions ofthe component images to form elements of a composite image that isdecodable using a lenticular lens. In FIG. 8, two component images 800,800′ are divided into elements 830, 830′ corresponding in shape andfrequency to the features of a decoder having “wavy” lenticules. Asbefore, the component images are created so as to be balanced around aparticular shade (or shades). The composite image 800″ is again formedby assembling subelements 832, 832′ from the component images 800, 800′.A zoom factor can be used if desired. In this example, the zoom factoris one, which indicates that the composite image elements are the samesize as the component image elements (i.e., the component image elementsare not shrunk). The approaches of collecting and ordering discussedherein may also be applied for a wavy decoder or any other type ofdecoder. In this example, the portion of the first component image,which is the light gray portion, may be taken from the same geometricalposition as the portion of the second component image, which is the darkgray portion. The portions of the component images may have equal size.The combined portions of the component images or the elements of thecomposite images may cover the area of a single decoding feature in thecomposite image.

If the portions of the component images used to create a composite imageare sufficiently small and if the phases are balanced along the samecolor shade, the techniques described herein may produce an image thatlooks like a tint, i.e. uniform color shade, when printed.

FIG. 9 illustrates a generalized method 900 of producing a compositeimage according to an embodiment of the invention. The method 900 beginsat S902 and at S904 a latent image is provided. Using the latent image,two or more component images are created at S906. As previouslydiscussed, these component images are formed so that at each position,the tonal values are balanced around a selected tonal value or tintdensity. At S908, the image components are used to produce a pluralityof image elements to be used to form a composite image. These compositeimage elements are formed and positioned according to a pattern andfrequency of the features of a decoder. As previously discussed, thecomponent elements may be positioned and sized based on a frequency thatmatches or is a multiple of the frequency of the decoder. In someembodiments, the component image elements are constructed by dividingthe composite image into non-overlapping elements or cells. In otherembodiments, the component image elements may be formed as overlappingelements or cells.

At S910, content from each element of each of the component images isextracted. In embodiments where the component images are divided intonon-overlapping elements, the action of extracting content may includesubdividing each element of each component image into a predeterminednumber of subelements. The image content from the subelements is thenextracted. The subelements from which content is extracted may be theinverse of the number of component images or a multiple thereof. Thus,if two component images are used, then half of the subelements areextracted from each element.

In embodiments where the component images are used to produceoverlapping elements, the content of each element may be extracted. Aspreviously described, a zoom factor may be applied to the extractedelements to produce subelements that can be used to form the compositeimage.

At S912, the extracted content from the component images is used to forma composite image. This may be accomplished by placing subelements fromeach of the components into positions corresponding to the positions inthe component images from which the content of the subelements wasextracted. The method ends at S914.

Any or all of the steps provided in method 900 and any variations may beimplemented using any suitable data processor or combination of dataprocessors and may be embodied in software stored on any data processoror in any form of non-transitory computer-readable medium. Once producedin digital form, the encoded composite images may be applied to asubstrate by any suitable printing, embossing, debossing, molding, laseretching or surface removal or deposit technique. The images may beprinted using ink, toner, dye, pigment, a transmittent print medium, asdescribed in U.S. Pat. No. 6,980,654, which issued Dec. 27, 2005 and isincorporated herein by reference in its entirety; a non-visible spectrum(e.g., ultraviolet or infrared) print medium as described in U.S. Pat.No. 6,985,607, which issued Jan. 10, 2006 and is incorporated herein byreference in its entirety.

It will be understood that there are a variety of ways in which balancedimage components may be constructed. In various embodiments, balancedcomponent image portions may be created by inverting the portions of onecomponent image to form the portions of the second component. If thisapproach is used, the component images may be balanced around 50%density, and the composite image will appear to the naked eye as a 50%tint. When printed or otherwise displayed, the elements of the compositeimage may be printed next to each other and the eye will average themout to (60%+40%)/2=50%. Another example for generating the compositeimage includes digitally encoding a darkened and brightened version ofthe color latent image. One component can be darkened by using theintensity/color curve designed for darkening, and the other componentcan be brightened in each location by the same amount as the firstcomponent was darkened. An alternative technique for blending colorsinto the composite image include transforming a color image into a colorspace that separates the image into intensity and color components, suchas Lab, Yuv, or HSi color space, and applying intensity/color curves asmentioned above in these color spaces. Other color spaces may be used.

In some embodiments of the invention, a tint based composite image maybe integrated or embedded into a visible image, such as any visible art.The composite image(s) may be hidden to the naked eye within the visibleimage, but rendered not hidden when a decoder is placed on the printedvisible image or composite image. All of the effects associated with thecomposite image (i.e. the appearance of floating, alternation ofcomponent image viewability, etc.) may be retained.

One approach to this is to apply a halftone screening technique asdiscussed above that uses the composite images as a screen file tohalftone the visible image. This technique may modify the elements ofthe composite image by adjusting the size of the element to mimic thedensities of the pieces of the visible image at the same positions. Inthis method, the composite image has no more than two intensity levelsin each of its color separations. The corresponding color separations ofthe composite image are used as screens for the visible image. If thecolor components of the composite image are not bilevel, they can bepreprocessed to meet this requirement.

FIGS. 10 and 11 illustrate an example of this approach. FIG. 10illustrates two component images 1000, 1000′ constructed based on ablock letter “USA” latent image, which are used to construct a compositeimage 1000″ formed from square elements of the two component images1000, 1000′. As discussed herein, the basic composite image appears assingle tone image to the naked eye. Magnification, however, shows thatthe composite image 1000″ is formed from a plurality of subelements.Each of these subelements is a square portion taken from a correspondingelement of one of the component images 1000, 1000′. It will beunderstood that all of these subelements are the same size and shape.The appearance of varying sized rectangles in the enlarged area occursas the result of the variation in content within the subelements.Placement of a corresponding decoder over the composite image 1000″“reassembles” this content so that the component images 1000, 1000′ withthe latent image can be viewed.

FIG. 11 illustrates a visible image 1110 along with a halftone 1110′ ofthe same image screened using the composite image 1000″ of FIG. 10. Theunmagnified half-tone image 1110′ appears unchanged to the naked eye.Magnification, however, shows that the image 1110′ is made up of thesquare elements of the composite image, which have been modifiedaccording to the tone density of the original image 1110. In effect, thecomposite image 1000″ of FIG. 10 is embedded within the visible image1110. When a decoder is placed over the encoded image (i.e., thehalftone artwork 1110′), the component images 1000, 1000′ will bevisible.

FIG. 12 illustrates another approach to hiding a latent image within avisible image 1200. As was previously discussed, component images 1210.1210′ may be formed by tonally balancing corresponding positions arounddifferent tone densities in different areas. This approach can be usedto create component images 1210, 1210′ from a visible image 1200 asshown in FIG. 12. One approach is to darken the visible image 1200 tocreate a first replica image and correspondingly lighten the visibleimage 1200 to create a second replica image. An area matching a latentimage may be masked from each of the replica images and replaced in eachcase by the content from the masked area of the other replica. In theexample illustrated in FIG. 12, the areas of the visible image 1200 thatalign with the letters “USA” (i.e. the latent image) are essentiallyswapped between the replica images to produce the component images 1210,1210′. The component images may then be sampled and combined to createthe composite image 1210″ using any of the techniques discussed herein.The composite encoded image 1210″ closely resembles the original primaryimage 1200, but with the hidden message “USA” being viewable using adecoder corresponding to the size and configuration of the elements usedto form the subelements of the composite image 1210″.

Another approach to hiding a latent image within a visible image is touse both the visible and latent images to create corresponding componentimages. This approach is illustrated in FIGS. 13 and 14. FIG. 13illustrates (in gray scale) a color visible image 1300 of a tiger, and acolor latent image 1310 of a girl. In this example, the visible image1300 is used to form four identical component images 1300A, 1300B,1300C, 1300D, which are divided into elements 1430A, 1430, 1430C, 1430Das shown in FIG. 14. A matching decoder may include a rectangular orelliptical lens, for example. As in previous examples, only a singleelement is shown for each component image, but it will be understoodthat the elements are formed over the entire component image. It willalso be understood that, for demonstration purposes, the elements inFIG. 14 are depicted much larger than actual elements used in themethods of the invention. In the illustrated embodiment, each of theelements of the four components is divided into subelements 1432A,1432B, 1432C, 1432D. Because, in this example, a total of six componentsare used to produce the composite image, the component image elementsare divided into six subelements.

It will be understood that, in practice, it is not actually necessary tocreate separate component images of the visible image. The visible imageitself can be used to produce the elements and subelements used toconstruct the composite image.

The latent image 1310 is used to produce two corresponding componentimages 1310A, 1310B. The second component image 1310B is produced as aninverse of the first component image 1310A. The first and secondcomponent images 1310A, 1310B are divided into elements 630E, 630F,which may be non-overlapping elements (as shown in FIG. 11) or asoverlapping elements like those shown in FIG. 3. As with the componentimages that correspond to the visible image, each of the elements of thelatent components 1310A, 1310B is divided into subelements 1432E, 1432B,1432C, 1432D. Again, six subelements are formed from each element.

In this example, the goal is for the visible image to be visible to thenaked eye and the latent image to be visible with the assistance of adecoder, which is configured to correspond to encoding parameters,including a frequency of the elements extracted from the visible andlatent component images 1300A, 1300B, 1300C, 1300D, 1310A, and 1310B.Thus, in constructing the composite image, the majority of thesubelements used are taken from the visible component images 1300A,1300B, 1300C, and 1300D that correspond to the visible image. In theillustrated example, four subelements (A1, B2, C4 and D5) of the sixsubelements used in each element 1422 of the composite image 1420 areextracted from the four visible component images 1300A, 1300B, 1300C,and 1300D that correspond to the visible image. The other twosubelements (E3 and F6) used in the element 1422 are extracted from thelatent composite images 1310A, 1310B that correspond to the latentimage. The subelements E3 and F6 are interlaced with the foursubelements A1, B2, C4, and D5 extracted from the visible image. Becausethe subelements E3 and F6 extracted from the latent image arecompensated such that an original image tint for one subelement isexchanged with an inverse image tint for the other subelement, thesubelements E3 and F6 will not be visible to the naked eye. In otherwords, the eye will mix up the corresponding subelements E3 and F6 intoa 50% tint. As in previous embodiments, the subelements used and theirplacement within the element 1422 of the composite image 1420 can vary.

Because the subelements that originate from the visible image 1300 arenot changed in any way, an observer will still see the image of thetiger in the composite image 1420 with a naked eye. Under a properlyoriented decoder, however, the composite image elements will be visuallygrouped so that, for some angles of view, the observer will see thevisible image 1300 (e.g., the tiger of FIG. 13), for other angles ofview, the observer will see the latent image 1310 (e.g., the girl ofFIG. 13), and for yet other angles of view the observer will see theinverse of the latent image 1310. In this way, the color latent image1310 and its inverse are hidden inside the color visible image 1300.Additional effects may be added to the decoded image by applying elementflipping and/or a zoom factor larger than one to the latent componentimages 1310A, and 1310B generated from the latent image 1310.

In a variation to the above embodiment, instead of using a majority ofsubelements from the visible image 1300 for each composite imagesubelement A1, B2, C4, D5, E3 and F6, the visible image 1300 can bepreprocessed to increase its contrast. This allows the reduction of thenumber of subelements that are extracted from the visible image 1300 inorder to hide the latent image 1310.

In any of the embodiments described herein, the visible and latentimages used to create a composite image may be binary, grayscale, colorimages, or a combination of any type of image. In this way, thecomponent images revealed with the decoder may be binary, grayscale orcolor images.

A Multi-Layered Decoder That Simultaneously Decodes Latent Image ColorComponents

As described herein, the composite image may include latent images thatare encoded into a visible image using two or more color components.While the composite image may include multiple color components, thecolor components may be blended to generate a monotone image. Forexample, blending equal amounts of Cyan tint, Magenta tint, and Yellow.Techniques described herein enable encoding and decoding of color latentimages from seemingly uniform visible images. The visible images includecontent variations such that the observer cannot correlate the colorsrevealed with the decoding device with colors seen by the unaided eye.According to one example, the latent images are divided into at leasttwo color component separations that correspond to color components thatare available in the visible image. The color separated latent imagesare encoded into the corresponding color components of the visible imagebased on encoding parameters that are determined by features of thematching decoder. For example, the encoding parameters may include arelative angle for depositing a particular color component and afrequency of decoding elements, such as lenses, used to decode thecomposite image, among other encoding parameters.

FIGS. 16 and 17 illustrate examples of multi-layer decoders, orrendering devices, having two layers. The elements (or lenticules) ineach layer of the multi-layer decoder are arranged according to aselected frequency or pattern of the corresponding latent image colorcomponent. The elements (or lenticules) in each layer of the multi-layerdecoder are further oriented to match the relative angle in which thelatent image color component was deposited onto the substrate. When theencoding parameters of the latent image are matched to the features ofthe corresponding rending layers, each layer of the latent image may besimultaneously decoded. One of ordinary skill in the art will readilyappreciate that more than two rendering devices may be used tosimultaneously decode latent images associated with more than two colorcomponents.

FIG. 16 illustrates components of a two layer decoder. The firstrendering device 1601 is shown in a side view 1602 and a bottom view1604. The second rendering device 1610 is shown in a side view 1612 anda top view 1614. As shown by the adjacent placement of the firstrendering device 1601 and the second rendering device 1610 in FIG. 16,the first layer elements 1605 are oriented approximately perpendicularto the second layer elements 1615. It follows that the two colorcomponent layers associated with the two latent images are oriented tomatch the angle of the corresponding first layer elements 1605 and thesecond layer elements 1615. Therefore, each layer of the latent imagesis decoded simultaneously to provide a multi-color decoded image.

While the first rendering device 1601 and the second rendering device1610 are illustrated to include linear lenses, one of ordinary skill inthe art will readily appreciate that the first rendering device 1601and/or the second rendering device 1610 may include non-linear lenses.Non-linear lens structures may include a wavy line structure, zigzagstructure, fish bone structure, arc-like structure, a free-hand shapedstructure, or the like. According to one example, the first renderingdevice 1601 and the second rendering device 1610 may include a same lensstructure or different lens structures. Furthermore, the multi-layeredlens may include layers formed using different technologies, such ashaving a first layer formed using a molded lens array and a second layerformed using a silkscreen printing process.

As illustrated in FIGS. 17A-17C, the first rendering device 1601 and thesecond rendering device 1610 may be positioned in various configurationsrelative to each other. The arrow 1700 shows the direction of view. Asillustrated in FIG. 17A, the first rendering device 1601 and the secondrendering device 1610 may be positioned so that the first layer elements1605 and the second layer elements 1615 face inwardly toward each other.When the first layer elements 1605 are oriented toward the image, thefirst layer elements 1605 will decode the image through the secondrendering device 1610. In this case, the second rendering device 1610will be positioned to physically contact the encoded image.

In a second example illustrated in FIG. 17B, the first rendering device1601 and the second rendering device 1610 may be positioned so that thefirst layer elements 1605 and the second layer elements 1615 faceoutwardly away from each other. In this configuration, the firstrendering device 1601 may be positioned slightly above the encoded imageto enable the first layer elements 1605 to focus on the encoded image.

In a third example illustrated in FIG. 17C, the first rendering device1601 and the second rendering device 1610 may be oriented in a samedirection so that both the first layer elements 1605 and the secondlayer elements 1615 face upward. In this case, the curvature of thefirst layer elements 1605 and the second layer elements 1615 may bedesigned so that the first layer elements 1605 and the second layerelements 1615 focus on the bottom surface of the multi-layered decoder.

In the above examples, the frequency of the first layer elements 1605and the second layer elements 1615 may be the same or different. Forexample, the frequency of the first layer elements 1605 and the secondlayer elements 1615 may be 250 lines per inch. Alternatively, thefrequency of the first layer elements 1605 and the second layer elements1615 may be 200 lines per inch for Layer 1 and 250 lines per inch forLayer 2.

A Single-Layer Decoder That Simultaneously Decodes Latent Image ColorComponents

As described herein, the composite image may include latent images thatare encoded into a visible image using two or more color components.While the composite image may include multiple color components, thecolor components may be blended to generate a monotone image. Forexample, blending equal amounts of Cyan tint, Magenta tint, and Yellowtint creates an image that appears to have a uniform brown tone.Techniques described herein enable encoding and decoding of color latentimages from seemingly uniform visible images, or visible images withvariations in their content where the observer cannot correlate thecolors shown with decoding device with colors seen by naked eye.

According to one example, the latent images are divided into at leasttwo color component separations that correspond to color components thatare available in the visible image. The color separated latent imagesare encoded into the corresponding color components of the visible imagebased on encoding parameters that are determined by features of thematching decoder. For example, the encoding parameters may include arelative angle for depositing a particular color component and afrequency of decoding elements, such as lenses, used to decode thecomposite image, among other encoding parameters.

FIG. 18 illustrates an example micro-array lens matrix 1800 configuredprovided on a single layer. The elements or micro-lens elements 1802 arearranged according to a selected frequency or pattern of thecorresponding latent image color component. For example Path 1 (1810)and Path 2 (1815) are illustrated to have a same frequency, while Path 3(1820) is illustrated to have a higher frequency. According to oneexample, frequency is controlled by adjusting a distance between rows ofmicro-array elements 1802 for a corresponding path. Increasing adistance between rows of micro-array elements 1802 may correspond tolowering a frequency, while reducing a distance between rows ofmicro-array elements 1802 may correspond to increasing a frequency.According to one example, the micro-lens elements 1802 may include asame lens structure or different lens structures.

The micro-lens elements 1802 are further oriented along one or more ofPath 1 (1810), Path 2 (1815) and Path 3 (1820) to match the relativeangle in which the latent image color component was deposited onto thesubstrate. While Paths 1-3 are illustrated to be linear paths, thisdisclosure supports non-linear paths. Non-linear paths may include awavy line path, zigzag path, fish bone path, arc-like path, a free-handshaped path, or the like. When the encoding parameters of the latentimage are matched to the features of the single layer micro-array lensmatrix 1800, each layer of the latent image may be simultaneouslydecoded. One of ordinary skill in the art will readily appreciate thatmore than three paths may be provided to simultaneously decode latentimages associated with more than three color components. One of ordinaryskill in the art will also readily appreciate that the micro-lenselements 1802 may be arranged in other matrix configurations thatsupport multiple decoding paths with equidistant lens elements thatmatch a frequency and angular orientation used for the encoding process.Such matrix configurations include a hexagonal grid configuration,concentric ring configuration, or other configurations.

According to another example, the encoding process may arrangemicro-lens elements 1802 to support variable frequencies. In this case,the so that along a path, the distance between the micro-lens elements1802 elements varies. According to one example, if the micro-lenselements 1802 are positioned along paths that correspond to linear pathsused for the encoding process, then the micro-lens elements 1802 willsample the encoded image and recreate the latent image. By samplingpieces of the segments rather than decoding an entire segment of theencoded image, the decoded image may appear to be slightly jagged.However, if a frequency of the encoding process and a frequency of themicro-lens elements 1802 are sufficiently high, such as greater than 140lines per inch, this effect may not be noticeable.

A Single-Layer Decoder That Simultaneously Decodes Frequency SampledColor Components

According to one example, the latent images are divided into at leasttwo color component separations that correspond to color components thatare available in the visible image. In this example, four colorcomponent separations are used and a linear lenticular decoding lens isprovided to decode a four color component composite image.

As illustrated in FIG. 19, the lenticular lines used in the encodingprocess may be divided into four subsets that match the four colorseparations provided in the visible image and the latent image. The foursubsets include black segments 1901, yellow segments 1902, magentasegments 1903, and cyan segments 1904. In other words, one fourth of thesegments may be used to encode black separation, another fourth of thesegments may be used to encode yellow separation, another fourth of thesegments may be used to encode magenta separation, and the last fourthof the segments may be used to encode cyan separation.

According to one example, the subsets 1901, 1902, 1903, 1904 may beinterleaved. For example, line numbers 1,5,9,13,17, etc. include thefirst subset of black segments 1901 corresponding to the blackcomponent. Line numbers 2,6,10,14,18, etc. include the second subset ofyellow segments 1902 corresponding to the yellow component. Line numbers3,7,11,15,19, etc. include the third subset of magenta segments 1903corresponding to the magenta component. Line numbers 4,8,12,16,20, etc.include the fourth subset of cyan segments 1904 corresponding to thecyan component. The color components of the latent image are encodedinto the appropriate subsets 1901, 1902, 1903, 1904. In this example,the frequency used for the encoding method is one fourth of the decoderfrequency. In this example, a same encoding angle is applied to each ofthe subsets 1901, 1902, 1903, 1904.

In FIG. 19, an image is illustrated with cyan, magenta, yellow, andblack color separations printed in a line screen at 25 degrees. Eachcolor component of the visible image is encoded with the correspondingcolor component of the latent image. When the decoder is placed over thecomposite image, the decoder will simultaneously decode all colorcomponents, including the black component, the yellow component, themagenta component, and the cyan component. The decoded composite imagereveals the composite color latent image.

This disclosure contemplates several variations to the above-describedmethod. For example, rather than using a same frequency for all colorcomponents, more line repetitions may be used for one of the colorseparations. This will result in a higher frequency for the selectedcolor separation. This disclosure further contemplates using differentscreening elements for different color separations. For example,straight segments may be used for some color separations and wavysegments may be used for other color separation. Another variationincludes arranging lenticular lenses or micro-array lens elements tofollow non-linear patterns, such as concentric rings pattern. Non-linearpatterns may be produced by dividing the decoder elements into subsets.The number of subsets may match the number of the color components ofthe latent image and the color separations of the latent image may beencoded into these subsets.

According to one example, the frequency sampled color components wouldbe applied to brighter images, including images having color separationswithin a 0-25% density range. This disclosure contemplates using anylens pattern to encode and decode color latent images, where differentcolor components of the latent image are encoded into the elements ofthe visible image that match the designated subsets of the decoderpattern. Each of the color separations of the encoding image is printedusing the same color separation from the latent image. For example, acyan color separation of the latent image is encoded into the cyan colorseparation of the visible image.

Creating Rainbow Effects Or Color Variations Using Multiple LatentImages

The above examples describe techniques for creating complex color latentimages for encoding into a visible image. For example, the complex colorlatent images may include different color components provided within thecomposite image. The degree to which decoded color latent image matchesthe color latent image used for encoding depends significantly on thequality and resolution of the device used to apply encoded image to thearticles.

For applications in which high quality and high resolution printers arenot available, such as printing passport images encoding personal data,it may be difficult to achieve consistent match of the colors betweencolor images used for encoding and color images decoded after applyingimages to the article. This may also be partly due to variation in thevisible image (for example, every passport photo is different). In thesecases, authentication may be accomplished, for example, by adding asecond latent image that provides color variations or vivid colorproperties to an encoded composite image, without necessary requiring agood color match between desired and decoded color images. This encodingprocess may be performed at processing speeds that are comparable to theunderlying processing speed needed to generate the personal informationfor embedding into the visible image.

To expedite the process of encoding color separations into the visibleimage, repetitive monochromatic latent images may be provided. Asdiscussed herein, an inversion process may be used to manipulate thelatent image or portions of the latent image. When the decoder is placedover the printed encoded visible image, color differences arediscernible between the latent image and the surrounding visible image.Alternatively, a process may be provided for changing the brightness ofthe latent image or portions of the latent image before encoding thelatent image into the particular color separation of the visible image.Changing the brightness of the latent image produces color differencesbetween the latent images and the surrounding visible image that arediscernible when the decoder is placed over the printed encoded visibleimage.

The processes of inverting latent images or changing the brightness ofthe latent image to encode the latent image into a visible image, suchas a photograph, do not provide consistent results when applied topersonal documents, such passports and driver's licenses. One reason isthat a subject's photographic image is unique so it follows that encodedphotographic image may include unique color variations when decodedusing the optical decoder. One technique that may be applied tostandardize the process of authenticating personal documents includesproviding a second latent image as described below.

FIG. 15 illustrates a visible image 1510 depicting a photograph of asubject, a first latent image having a first pattern that is generatedusing a red color component 1515, a first latent image having a firstpattern that is generated using a blue color component 1520, and asecond latent image 1525 having a second pattern that is generated usinga green color component 1520. As illustrated, the content of the firstlatent images 1515, 1520 is different than the content of the secondlatent image 1525. One of ordinary skill in the art will readilyappreciate that other content differences may be provided between thefirst latent image and the second latent image.

According to one example, the first latent image 1515 illustrates theblock letters “JANE” which are rendered against a dark background, theblock letters “JANE” being generated using a red color component. Thefirst latent image 1520 illustrates the block letters “JANE” which arerendered against a dark background, the block letters “JANE” beinggenerated using a blue color component. One of ordinary skill in the artwill readily appreciate that different content may be provided for thefirst latent image.

The second latent image 1525 illustrates block letters “JANE” which arerendered against a white background 1527, the block letters “JANE” 1526being generated using a green color component. The second latent image1525 further illustrates block letters “JANE” which are rendered againsta dark background 1528, the block letters “JANE” being generated basedon the absence of ink. One of ordinary skill in the art will readilyappreciate that different high contrast content may be provided for thesecond latent image.

Using the techniques described herein, the composite image 1530 isgenerated by encoding the latent images 1515, 1520, 1525 into thevisible image 1530. Since the content provided in the second latentimage 1525 offers more variations as compared to the content provided inthe first latent images 1515, 1520, the color component of the secondlatent image 1525 introduces color variations in the encoded compositeimage 1530. As illustrated by the decoded image 1540, when the encodedcomposite image 1530 is viewed through a decoder, the variations in thegreen color component contributed by the second latent image 1525combine with the red color component contributed by the first latentimage 1515 and the blue color component contributed by the first latentimage 1520. As a result, introducing the second latent image 1525provides color variations and vivid color properties to an encodedcomposite image 1530. One of ordinary skill in the art will recognizethat more than two latent images may be provided for encoding into thevisible image. Furthermore, one of ordinary skill in the art willrecognize that variations in the latent image can be introduced to anycolor component.

A Digital Decoding Device That Decodes And Concurrently Displays LatentImages Encoded Having Two Or More Color Separations

When the composite images produced according to the various embodimentsof this disclosure are printed or otherwise associated with an article,the component images used to produce the composite images may be viewedby application of a corresponding decoder. For example, the decoder mayinclude a software decoder programmed to decode and concurrently displaytwo or more color separations that correspond to two or more componentimages. An example software decoder is described herein. The componentimages may be viewable through the use of a software-based decoder.,such as those described in U.S. Pat. Nos. 7,512,249 (“the '249 Patent”)and 7,630,513 (“the '513 Patent”), the complete disclosures of which areincorporated herein by reference in their entirety. As described in the'249 Patent and the '513 Patent, an image of an area where an encodedimage is expected to appear can be captured using an image capturingdevice such as a scanner, digital camera, or telecommunications deviceand decoded using a software-based decoder. In some embodiments, such asoftware-based decoder may decode a composite image by emulating theoptical properties of the corresponding decoder lens. Software-baseddecoders also may be used to decode a digital version of a compositeimage of the invention that has not been applied to an article.

According to one example, the latent image is divided into two or morecolor separations before being embedded within the visible image. Thetwo or more color separations of the latent image may correspond tocolors that are not present in the visible image. Thus, each colorseparation of the latent image may be encoded into different colorseparations of the visible image. For example, each color separation maybe independently encoded into the visible image using encodingtechniques described herein.

In an alternative example illustrated in FIG. 20, the latent image colorseparations 2025, 2027, and 2029 may be encoded into multiple halftonescreens that are positioned at different angles with respect to ahorizontal line 2022. The different angles are represented by segments2045, 2047, and 2049. The multiple halftone screens may be printed usinga same color. For example, the line screens for the latent image may beprinted using black ink. Additionally, for a latent image having threecolor separations, the red component may be encoded using a line screenoriented at {acute over (α)}1=15 degrees; a green component may beencoded using a line screen oriented at {acute over (α)}2=30 degrees;and a blue component may be encoded using a line screen oriented at{acute over (α)}3=60 degrees. If bidirectional screens are used, such asa dot screen, two latent images may be encoded into one screen andoriented at a 90 degree angle relative to each other.

FIG. 20 illustrates a digitally encoded image 2010 that includes avisible image 2020 and a latent image having three corresponding colorcomponent separations 2025, 2027, and 2029. The visible image 2020 maybe generated using black ink, gray-scale or multi-color ink. The colorcomponent separations 2025, 2027, and 2029 are embedded within thevisible image 2020. According to one example, the color componentseparations 2025, 2027, and 2029 may be separately encoded and thenmerged or embedded into the visible image 2020. Alternatively, theprocess may be performed so that the color component separations 2025,2027, and 2029 are encoded as they are embedded. In any event, the colorcomponent separations 2025, 2027, and 2029 are not viewable to anunaided eye without a software decoding device 2030.

According to one example for embedding or merging the latent image withthe visible image, the visible image may be sampled to produce a visibleimage having a first periodic pattern at a first predeterminedfrequency. The latent image having two color components is then mappedto the visible image so that the first periodic pattern of the visibleimage is altered at locations corresponding to locations in the latentimage having image content depicted with the two color components. Thealterations to the visible image are sufficiently small that they aredifficult for the unaided human eye to discern. However, when thesoftware decoding device 2030 displays the encoded image at a frequencythat correspond to the first predetermined frequency, the softwaredecoding device 2030 captures the alterations in the visible image todisplay the latent image.

According to another approach for embedding or merging the latent imagewith the visible image, the first periodic pattern is first imposed onthe latent image having two color components rather than on the visibleimage. In this case, the alterations are provided on the content that isassociated with the latent image having two color components. The latentimage is then mapped to the visible image and the content of the visibleimage is altered pixel by pixel based on the content of the encodedlatent image. Other methods are available for embedding or merging thelatent image with the visible image.

The software decoding device 2030 decodes the latent images 2025, 2027,and 2029 while displaying the encoded image 2010 on a graphical userinterface (“GUI”). The digital decoding system 1800 described below andillustrated in FIG. 18 performs image processing and may be configuredto assign a designated color to each latent image, including monochromelatent images. For example, three monochrome latent images may beprovided within a visible image. A first monochrome latent image may beoriented at 15 degrees, a second monochrome latent image may be at 30degrees, and a third monochrome latent image may be at 60 degrees. Thesoftware decoding device 2030 may be configured to detect theorientation of each monochrome latent image and assign a correspondingcolor component to the color separation. Accordingly, the softwaredecoding device 2030 may assign a color red to the first monochromelatent image oriented at 15 degrees, a color blue to the secondmonochrome latent image oriented at 30 degrees, and a color green to thethird monochrome latent image oriented at 60 degrees. The softwaredecoding device 2030 may merge the designated colors to generate acomposite color latent image for display to the user. For example, theassigned colors may be merged to yield a desired color shade. One ofordinary skill in the art will recognize that any combination of colorsmay be used and any desired color shades may be provided.

FIG. 21 illustrates an exemplary digital decoding system 2100 forauthenticating an encoded image affixed to an article. An encoder device2110 is provided to include an encoder module 2112 and an embeddingmodule 2114 that communicate with an encoding information database 2140via a network 2120. The encoder module 2112 and the embedding module2114 are configured to perform encoding and embedding operations,respectively. The color encoding module 2112 also may be programmed togenerate an encoded image to be affixed to the article, based onencoding parameters, the visible image, and the latent image. An encoderinterface module 2150 is provided to serve as an interface between auser or document processing module (not shown) and the encoder device2110. The color encoding module 2112 may be configured to store theencoding parameters, the visible image, and the latent image in theencoding information database 2140 for subsequent use in authenticatingthe digitally encoded image.

The color encoding module 2112 also may store the encoded image in thedatabase 2140 and/or return the encoded image to the encoder interfacemodule 2150. The color encoding module 2112 further may provide thelatent image to the embedding module 2114, which is adapted to embed thelatent image into the visible image. The encoded image with the embeddedlatent image may be returned to the encoder interface module 2150.

The software decoder or authenticator 2130 may include a decoding module2132 and an authentication module 2134 that may be in communication withthe encoding information database 440. The decoding module 2132 isadapted to retrieve the encoding parameters and/or the encoded imagefrom the encoding information database 2140. The decoding module 2132decodes the digitally encoded image using the encoding parameters. Thedecoding module 2132 also may be adapted to receive the encoded image tobe authenticated and extract the latent image. The latent image may beobtained from an authenticator interface 460 that is adapted as aninterface between an authentication requestor and the authenticator2130. After decoding the encoded image, the decoding module 2132 mayreturn the decoded image to the authenticator interface and/or forwardthe decoded image to the authentication module 2134. The authenticationmodule 2134 is adapted to extract latent image from the decoded imagefor comparison to authentication criteria, which may be derived frommultitude of image features, such as shape descriptors, histograms,coocurence matrices, frequency descriptors, moments, color features etc.The authentication module 2134 may further be adapted to determine anauthentication result and return the result to the authenticatorinterface. The authentication module 2134 may include OCR software orbar-code interpretation software to extract information from thearticle. One of ordinary skill will understand that the color encodingmodule 2112, the embedding module 2114, the decoding module 2132, theauthentication module 2134, the encoding information database 2140, theencoder interface module 2150 and the authenticator interface module2160 may be distributed among one or more data processors. All of theseelements, for example, may be provided on a single user data processor.Alternatively, the various components of the digital decoding system2100 may be distributed among a plurality of data processors inselective communication via the network 2120.

Additionally, software-based decoders enable encoding of compositeimages using multiple color separations and geometrically complicatedelement patterns. Some lens element patterns and shapes may be difficultor impractical to physically manufacture as optical lenses. Thesedifficulties, however, do not apply to the techniques used to create theimages of the present invention and, moreover, do not apply tosoftware-based decoders. The software-based decoder may be designed withflexibility to enable device users to adjust the decoding parameters.The methods described herein can make use of a “software lens” havinglens elements that have a variable frequency, complex and/or irregularshapes (including but not limited to ellipses, crosses, triangles,randomly shaped closed curves or polygons), variable dimensions, or acombination of any of the preceding characteristics. The methods of theinvention can be applied based on the specified lens configuration, evenif this configuration cannot be physically manufactured. The methods ofcreating composite images from component images as described herein arebased on the innovative use of geometric transformations, such asmapping, scaling, flipping etc, and do not require a physical lens to becreated for this purpose. Providing a software-based lens configuration,or specification, allows a user to implement desired software lenses.Some or all of the characteristics of the software lens could then beused by a software decoder to decode the encoded composite image toproduce decoded versions of the component images used to create thecomposite image.

The decoder also may include a rendering device that is configureddecode the latent images. The rendering device may include a lensconfigured in any shape and having lens elements arranged in anypattern. For example, the lens may include lens elements arranged in asymmetrical pattern, an asymmetrical pattern, or a combination of both.The lens may further include lens elements that are arranged in aregular pattern or an irregular pattern.

According to one example, the rendering device may include a lenticularlens having lenticules arranged in a straight line pattern, a wavy linepattern, a zig-zag pattern, a concentric ring pattern, a cross-linepattern, an aligned dot pattern, an offset dot pattern, a grad frequencypattern, a target pattern, a herring pattern or any other pattern.Alternatively, the rendering device may include lenses, such as a fly'seye lens, having a multidimensional pattern of lens elements. Themultidimensional pattern may include a straight line pattern, a squarepattern, a shifted square pattern, a honey-comb pattern, a wavy linepattern, a zigzag pattern, a concentric ring pattern, a cross-linepattern, an aligned dot pattern, an offset dot pattern, a grad frequencypattern, a target pattern, a herring pattern or any other pattern.Examples of some of these decoding lenses are illustrated in FIG. 22.

It will be readily understood by those persons skilled in the art thatthe present invention is susceptible to broad utility and application.Many embodiments and adaptations of the present invention other thanthose herein described, as well as many variations, modifications andequivalent arrangements, will be apparent from or reasonably suggestedby the present invention and foregoing description thereof, withoutdeparting from the substance or scope of the invention.

While the foregoing illustrates and describes exemplary embodiments ofthis invention, it is to be understood that the invention is not limitedto the construction disclosed herein. The invention can be embodied inother specific forms without departing from its spirit or essentialattributes.

1. A computer-implemented method of encoding a latent image into avisible image based on encoding parameters, the latent image having twoor more color components that are simultaneously revealed upon placing adecoder over an encoded image, the decoder having decoding parametersthat match the encoding parameters, the method comprising: generating,via a processor, a first image associated with a first color component,the first image having a first pattern of elements that are manipulatedbased on a corresponding color component provided in the latent image;assigning a first angle to the first image; generating a second imageassociated with a second color component, the second image having asecond pattern of elements that are manipulated based on a correspondingcolor component provided in the latent image; assigning a second angleto the second image; aligning the first image by orienting the firstpattern of elements according to the first angle; aligning the secondimage by orienting the second pattern of elements according to thesecond angle; and superimposing the aligned first image and the alignedsecond image to render the encoded image, the encoded image beingvisually similar to the visible image when viewed with an unaided eye.2. The computer-implemented method of claim 1, wherein the first patternof elements and the second pattern of elements are configured accordingto a first encoding frequency and a second encoding frequency,respectively.
 3. The computer-implemented method of claim 1, wherein thefirst pattern of elements and the second pattern of elements aremanipulated according to a phase shifting operation.
 4. Thecomputer-implemented method of claim 1, wherein superimposing thealigned first image and the aligned second image includes overlaying afirst halftone screen patterned according to the first image and asecond halftone screen patterned according to the second image.
 5. Thecomputer-implemented method of claim 1, wherein the first pattern ofelements include at least one of a wavy structure, a zigzag structure, afish bone structure, and an arc structure.
 6. The computer-implementedmethod of claim 1, wherein the second pattern of elements include atleast one of a wavy structure, a zigzag structure, a fish bonestructure, and an arc structure.
 7. The computer-implemented method ofclaim 1, wherein the first image and the second image are monotoneimages and the decoder assigns a color component during decoding.
 8. Acomputer-implemented method of encoding a latent image into a visibleimage based on encoding parameters, the latent image having two or morecolor components that are simultaneously revealed upon placing a decoderover an encoded image, the decoder having decoding parameters that matchthe encoding parameters, the method comprising: obtaining, via aprocessor, a latent image having at least two color components;generating an inverse of the latent image having inverse color values;determining a pattern of latent image elements for each color componentof the latent image, the pattern including an element configuration andat least one element frequency corresponding to the decoding parameters,the latent image elements providing content information; andconstructing the encoded image having a pattern of latent image elementsthat include the at least one element frequency corresponding to thedecoding parameters.
 9. The computer-implemented method of claim 8,further comprising screening the visible image to produce a half-toneimage of the visible image having the latent image incorporated therein,the latent image being non-viewable to an unaided eye, but viewablethrough the decoder when the decoder is placed over the encoded image.10. The computer-implemented method of claim 8, further comprising afirst screen of the half-tone image corresponding to the first colorcomponent, the first screen defining the first pattern of latent imageelements to include a first frequency that is at least two times greaterthan the at least one element frequency.
 11. The computer-implementedmethod of claim 10, further comprising a second screen of the half-toneimage corresponding to the second color component, the second screendefining the second pattern of latent image elements to include thesecond frequency that is at least two times greater than the at leastone element frequency.
 12. The computer-implemented method of claim 8,wherein at least a portion of the latent image elements include ageometric shape selected at least one of a polygon, an ellipse, apartial ellipse, a circle, and a partial circle.
 13. Thecomputer-implemented method of claim 8, wherein the pattern of latentimage elements for each of the component images includes at least one ofa wavy structure, a zigzag structure, a fish bone structure, and an arcstructure.
 14. A computer-implemented method of encoding two latentimages into a visible image based on encoding parameters, the latentimages having different content that is associated with two or morecolor components to generate a color effect that is revealed uponplacing a decoder over an encoded image, the decoder having decodingparameters that match the encoding parameters, the method comprising:generating, via a processor, a first image associated with a first colorcomponent, the first image having a first pattern of elements that aremanipulated based on a corresponding color component provided in thelatent image; generating a second image associated with a second colorcomponent, the second image having a second pattern of elements that aremanipulated based on a corresponding color component provided in thelatent image, the second latent image having different content than thefirst latent image; and superimposing the first image and the secondimage to render the encoded image, the encoded image being visuallysimilar to the visible image when viewed with an unaided eye.
 15. Thecomputer-implemented method of claim 14, wherein the first pattern ofelements and the second pattern of elements are configured according toa first encoding frequency and a second encoding frequency,respectively.
 16. The computer-implemented method of claim 14, whereinthe first pattern of elements and the second pattern of elements aremanipulated according to a phase shifting operation.
 17. Thecomputer-implemented method of claim 14, wherein superimposing thealigned first image and the aligned second image includes overlaying afirst halftone screen patterned according to the first image and asecond halftone screen patterned according to the second image.
 18. Thecomputer-implemented method of claim 14, wherein the first pattern ofelements include at least one of a wavy structure, a zigzag structure, afish bone structure, and an arc structure.
 19. The computer-implementedmethod of claim 14, wherein the second pattern of elements include atleast one of a wavy structure, a zigzag structure, a fish bonestructure, and an arc structure.
 20. The computer-implemented method ofclaim 14, wherein, the second latent image having different content thanthe first latent image renders the second color component as differentfrom the first color component.